Relatively large reusable containers are utilized by manufacturers to ship a variety of different products to their customers. For example, in the automobile industry, a plant assembling a particular automobile might utilize a number of different parts manufacturers. These manufacturers ship their respective parts to the plant in reusable containers where the parts are then assembled together into a finished automobile. The reusable containers are often returned to the parts manufacturers for use in further shipments.
Generally, construction of such shipping containers includes a pallet base, a cover and a sleeve pack which is situated between the base and cover to form the sidewalls of the container.
Such a design provides a versatile and lightweight shipping container which may be reused time and again. The vast majority of sleeve packs used today are made of heavy grades of triple wall corrugated paper, such as paper in the 1,000 pound bursting strength range. Such paper wall sleeve packs are functional if kept dry; however, as may be appreciated, moisture damages the strength of the paper wall and degrades the overall reliability of the sleeve pack. Accordingly, there is a need for a sleeve pack which can be stored outdoors as necessary when indoor storage space is not available.
Plastic sleeves have been utilized for weather-proof containers; however, the existing plastic sleeve packs have generally been inadequate. Specifically, the single layer plastic making up the sleeves is not capable of achieving adequate stacking strength, and therefore, several sheets of the single wall plastic material have to be laminated together. Often even the laminated sheets are not strong enough to support the stacking loads required, and they have to be reinforced by another material. The increased number of sheets and strengthening layers increases the expense of the containers and the complexity of their assembly.
Sleeve packs, whether plastic or paper, generally require reinforcing structures at their corners to hold the sleeve pack sidewalls together and to provide adequate support for the stacked loads. When shipped and stored, numerous containers will usually be stacked upon one another. The prior art shows several different corner support structures for reinforcing a container and enhancing its support strength. For example, the patent of Kidd, U.S. Pat. No. 4,643,314 discloses a container construction which utilizes hinged corner elements formed from a web extending between two cup-shaped structures. However, the sidewalls must be secured to the cup-shaped structures by adhesion requiring some sort of bonding adhesive and an additional and messy step when fabricating the sleeve pack. Furthermore, the strength of construction depends upon the adhesive bond.
The patent of Webb, U.S. Pat. No. 4,673,087 discloses a reusable container system having sidewalls with endmost strips that grip T-shaped ribs formed in the corner connectors. Such a design is both difficult to assemble and also expensive to manufacture as the sidewall material has to be specially formed to integrally fit with the ribs of the corner connector. Furthermore, assembly requires proper alignment of the strips and ribs.
The patent of Carter et al, U.S. Pat. No. 4,700,862 discloses a sidewall structure for a stackable bin. However, the corner structure is nothing more than an extension of the sidewall and must be adhesively bonded to the adjacent sidewall. As may be appreciated, such a design is both impractical from an assembly standpoint because of the necessity of adhesive, and inherently weak, as the support structure is essentially just additional sidewall material as opposed to a stronger, more rigid structure.
The container wall sleeves and corner hinges of Francis, Jr. et al, U.S. Pat. No. 4,828,132 requires inner and outer sidewall panels and a corner member which is capable of gripping two panels simultaneously. The increased number of panels increases the cost of the sleeve as well as the difficulty and time required to assemble and disassemble such a sleeve from its component parts. German Patent No. 1298440 discloses solid sidewalls which include a slot machined into the sidewall edges. An inside latching structure of the corner connector fits inside the slot to hold the sidewalls in the corner connector. This construction requires special side panels specifically constructed for the particular reinforcing corner structures of the container making the container more expensive to manufacture.
Accordingly, there is a need for a simple sleeve pack with corner structures which may be assembled quickly, easily, and without additional parts, adhesives or critical alignments. It is also desirable to have a sleeve pack which may be assembled starting with essentially flat sidewalls that do not have to be specially formed or molded to cooperate with the corner structures. It is further desirable that the pack be readily assembled and disassembled when necessary and have adequate supporting strength at the corners.
Additionally, there is also a need for a sleeve pack assembly which is easily recyclable. More specifically, the component parts of the sleeve pack should be able to be broken down quickly into individual material units which might be recycled and reused. The growing concern over the environment has made recyclability of a product a desirable feature. Furthermore, although recycling is not mandatory in the United States, it is foreseeable that the United States may adopt a practice where a container must be constructed such that it is easy to break down into separate recyclable pieces, an approach which has already been adopted in Europe.
There is also a need for a durable, collapsible sleeve pack which may be quickly and easily assembled from its component parts and then readily assembled into a collapsible and reusable container. Collapsible sleeve packs and containers are particularly important because they may be collapsed and return-shipped to the manufacturer in a form which occupies only a fraction of the volume occupied by the completely assembled container. Generally, shipping containers may be shipped back to the parts manufacturer and reused; however, the return shipping is relatively expensive because empty uncollapsed containers take up the same shipping volume as containers filled with parts. The cost of shipping and storage is determined by volume, and therefore, the same cost is incurred for an empty container as for a full container. Therefore, if the sleeve pack may be collapsed when the container is disassembled, it will amount to a substantial savings in return shipping costs.
Generally, collapsible sleeve packs have two opposing sidewalls which are hinged at their center. All of the end walls are then attached together into a sleeve pack at the corners by hinging corner structures. To collapse such a sleeve pack, the hinged sidewalls are hinged inwardly at their centers and sandwiched between the unhinged sidewalls. The hinging corner structures allow the collapsed sleeve pack to lie flat and occupy a volume which can be as little as 10% to 25% of the volume occupied by the assembled sleeve pack and container.
However, like the rigid containers of the prior art, the prior art collapsible containers utilize corner support structures which are difficult to assemble and disassemble with the various sidewalls. Furthermore, the prior art collapsible containers require rigid hinged structures at the centers of the hinging sidewalls further increasing the cost, weight, and complexity of the sleeve pack and the overall difficulty of its assembly. As a result, there is further a need for a collapsible sleeve pack which may be assembled and disassembled easily and quickly without adhesives, additional external parts, or special tools. Further it is desirable to have a sleeve pack which starts with ordinary flat sidewalls that are die cut and need not be specially formed or molded to have attaching structures. There is further need for a collapsible sleeve pack which meets all of these objectives and still provides ample support strength for use with stacked shipping containers.